Diagnostic Techniques Flashcards
Simplest and easiest technique to facilitate detection of intestinal parasites that infected subjects pass in their feces
Direct Fecal Smear (DFS)
What are the reagents used for DFS?
Normal Saline Solution (NSS: 0.85%) and Lugol’s Iodine
Most common sample for parasitology
Stool
Characteristics determined in macroscopic analysis
Color, consistency, mucus & blood presence, adult worms present
Routine procedure for microscopic analysis
DFS
Most ideal technique for microscopic analysis
Permanent staining
Increases the sensitivity especially if the parasite is in low count
Concentration technique
How many mg of stool should be put in the glass slide?
2 mg
Quantifies the egg can correlate the severity of the disease with the intensity of the infection and can assess the efficacy of treatment
Kato-Katz Technique
True or False: Kato-Katz Technique can be used for all parasites
False. This is not applicable to all.
What are the primary parasites used in Kato-Katz Technique?
Hookworm
Ascaris lumbricoides
Trichuris trichiuria
*can also be useful for Schistosoma
Unit used when conducting Kato-Katz
eggs per gram stool (epg)
What is the role of glycerine?
Clearing agent
For how long should the cellophane strips be soaked into glycerine before procedure?
24 hours prior to use
How long are hookworm eggs visible?
30-60 minutes
How long are A. lumbrocoides and T. trichiuria eggs visible?
months
How long are schistosome eggs recognizable?
Several months; examination preferred 24 hours within slide preparation
What is the amount of stool and epg for template with Diameter: 9 mm
Thickness: 1 mm?
50 mg; count x 20
What is the amount of stool and epg for template with Diameter: 6 mm
Thickness: 1.5 mm?
41.7 mg; count x 24
What is the amount of stool and epg for template with Diameter: 6.5 mm
Thickness: 0.5 mm?
20 mg; count x 50
What are the classifications of intensity of infection in A. lumbricoides?
light: 1-4,999 epg
moderate: 5,000-49,999 epg
heavy: more than or equal to 50,000 epg
What are the classifications of intensity of infection in T. trichiuria?
light: 1-999 epg
moderate: 1,000-9,999 epg
heavy: more than or equal to 10,000 epg
What are the classifications of intensity of infection in hookworms?
light: 1-1,999 epg
moderate: 2,000-3,999 epg
heavy: more than or equal to 4,000 epg
What are the classifications of intensity of infection in S. mansoni?
light: 1-99 epg
moderate: 100-399 epg
heavy: more than or equal to 400 epg
What is the gold standard for malarial parasites?
thick and thin smear
What are the organisms detected by thick and thin smear?
Babesia, Hemoflagellates, Trypanosoma, Filarial nematodes (microfilaria)
Used to determine if parasite is present; more sensitive; and is the first priority
thick blood smear
Used to confirm the Plasmodium species present
thin blood smear
Needs dehemoglobinisation by dipping in water
thick blood smear
Fixed with methanol
thin blood smear
What is the formula for parasitemia?
% parasitemia = (parasitized RBCs/total RBCs) x 100
What should be done if the parasitemia is high?
examine 500 RBCs
What should be done if the parasitemia is low?
examine 2000 RBCs
Also called “scotch tape” swab
Cellophane Swab
Primary parasite detected by cellophane swab
Enterobius vermicularis (pinworm) eggs
Time of collection in cellophane swab
early in the morning before the patient washes or defecates
How many negative tests should be done before pinworm infection is ruled out?
five (5)
Where is E. vermicularis mostly recorvered?
Perianal swab; low recovery in stool
What is the causative agent of taeniasis?
Taenia solium or Taenia saginata
Segments that causes apolysis that releases eggs in the process
Proglottid
Preferred sample for taeniasis
Stool
Dissolves lipid content and other debris in concentration techniques
Ethyl acetate
Easier to perform, routinely done, and more general
Sedimentation
More recommended and cleaner procedure, but is more expensive
Flotation
Filter paper with stool is dipped with water and the water is examined for filariform larva (L3)
Harada-Mori Filter Paper Culture
Like Harada-Mori, but more stool is used and examines filariform larva (L3)
Baermann Funnel Culture
Parasites examined by Harada-Mori and Baermann Techniques
Hookworm and Strongyloides
Blood concentration technique for microfilaria (sedimentation/thick film)
Knott’s Concentration Technique
What is the ratio of blood to reagent in Knott’s concentration technique?
1mL venous blood + 10mL 2% formalin centrifuged 500xg 10 mins
Used for schistosomes ; positive result is bulging of eggs
Circumoval Precipitin Test (COPT)
Reagent and sample in COPT
lyophilized S. japonicum eggs + patient’s serum
An inhibition test for trophozoites where the positive result is the non-bonding of dye
Sabin-Feldman Dye Test
Infection detected by Sabin-Feldman Dye Test
Toxoplasma gondi infection
How is Toxoplasma gondi transmitted?
transmitted through infection from cats and crosses the placental barrier, which makes it a fatal for pregnant and may cause cerebral defects and blindness
Reagent for Sabin-Feldman Dye Test
toxoplasma + patient’s serum + methylene blue dye
